Attempt #1 to Fix Issue #24

1. Make MDP control messages always first
in olsr packets.

2. Set originator/destination based on the
actual outgoing interface, not the main
address. This requires that we add a
parameter to the packet transformation
function (prototype and our implementation).

3. Initialize memory to 0.
Merge pull request #25 from hawkinswnaf/mdp-multi-iface

Attempt #1 to Fix Issue #24. Tested by @jheretic.